1. Field of the Invention
This invention relates to air and gas cleaners, and more particularly to air cleaners having replaceable filter elements that include an integrated or connected sorption filter.
2. Description of the Prior Art
In air filter and air and gas cleaner systems it is sometimes necessary to have a particulate filter to remove suspended particulate material from the air or gas combined with a sorbent filter to remove odors and gaseous and/or vaporous impurities. While the particulate filter may be effective in removing dust and particulate impurities in the air stream, it does not effectively remove such odors or gaseous and/or vaporous impurities. The sorbent filter is a vapor or vapor/gas phase filter, usually formed of carbon particles, which has the capability of removing vapor or gas molecules from the air stream that can cause odors or odorless, harmful, non-desirable compounds, and which may otherwise contaminate the air flow. The sorbent filter may work by adsorption or chemisorption.
For example, in ventilation systems for enclosed cabins, such as those used by the operators of agricultural equipment, effective air filtration is important because of the dust and agricultural chemicals encountered. Likewise, in commercial aircraft, effective air filtration is important due to contaminants and odors which may be contained in the aircraft cabin, such as body odors, cooking odors and phenolics from upholstery and interior material. Air filters should be effective in removing dust and particulate material from the air, and for this purpose high efficiency particulate air (HEPA) filters or ultra low penetration air (ULPA) filters are desirable. In addition, a sorption filter is desirable to remove unwanted gaseous or vaporous chemicals in the air flow. However, a sorption filter usually requires additional equipment to channel the air flow through a layer of sorbent material.
In addition, it is usually very difficult to provide layers of sorbent material in conventional filter air streams, since the sorbent material is often loose particles or granules or spherical pieces of carbon material which tend to settle. When the particles settle, it causes "channeling" which substantially reduces the effectiveness of the sorption filter. Carbon beds have utilized several different approaches to reduce the effects of carbon bed settling, such as pressure pads, spring-loaded follower plates, and other devices. However, all of these approaches require additional bulky and complex equipment.